Patent GB-1126363-A (GB)
Title: Hydrostatic power transmission
IPC: B60K17/10
Filed: 1965-09-17
Abstract: 1,126,363. Hydrostatic transmission ; Bowden mechanism. Y. KUZE. 17 Sept., 1965 [24 Sept., 1964], No. 39708/65. Headings F2C, F2D and F2K. A hydrostatic transmission for a vehicle comprises an engine driven variable displacement swash-plate pump 9 in closed-circuit with two fixed displacement swash-plate motors 7, 7<SP>1</SP> driving output shafts 8, 8<SP>1</SP>. The supply and return lines between the pump and motor are formed in a three-part block 11, 37, 38 and in rotatable motor valve plates 42, 42<SP>1</SP> which are rotated through 180 degrees to reverse the direction of the motors 7, 7<SP>1</SP>. The pump swash-plate 18 is biased by a spring 103 to its maximum displacement position and is automatically moved towards its zero displacement position by system pressure acting through a valve 107 on a differential servo-piston 96. The spool 110 of the valve 107 is connected to a forwardneutral reverse lever (120) and to a brake pedal so that when the lever (120) is moved to a neutral position as the brake pedal is depressed the valve spool 110 is moved left to vent a line 129 to one side 100 of the servo piston whereupon the swash-plate is moved to its zero displacement position. Rotation of the motor valve plates 42, 42<SP>1</SP> is controlled by valves 108, 109, 109<SP>1</SP> which selectively supply system pressure to differential pistons 82, 83, 86; 82<SP>1</SP>, 83<SP>1</SP>, 86<SP>1</SP> acting through balls 79 on the valve plates. With the valves 108, 109, 109<SP>1</SP> in the positions shown liquid from the high pressure side of the transmission is supplied to cylinders 81, 81<SP>1</SP> whereupon pistons 83, 83<SP>1</SP> move the valve plates 42, 42<SP>1</SP> to the forward drive position. The valve 108 is connected to a forward-neutral-reverse lever (120) (Fig. 4, not shown) which when moved to the neutral position moves the valve 108 to a position in which pressure liquid is supplied to both cylinders 80, 81; 80<SP>1</SP>, 81<SP>1</SP> and the larger pistons 82, 82<SP>1</SP> rotate the valve plates 42, 42<SP>1</SP> through 90 degrees whereupon the pistons 83, 83<SP>1</SP> abut pistons 86, 86<SP>1</SP>. With the lever 120 in the reverse position the valve 108 supplies pressure liquid to the cylinders 80, 80<SP>1</SP> alone whereupon the pistons 82, 82<SP>1</SP> rotate the valve plates 42, 42<SP>1</SP> through 180 degrees from the forward drive position to effect reverse rotation of the motors. When the valve 108 is in the forward drive position shown the forward-neutral-reverse valves 109, 109<SP>1</SP> may be used to control the motors individually to assist steering and starting with one wheel on soft ground. The valves 109, 109<SP>1</SP> may be operated electrically by push-buttons or a cam operated switch. A link 121 between the valves 107, 108 moves the valve 108 to its neutral position when the pedal is depressed or when the forward-reverse lever (120) is moved to its neutral position. An engine driven pump P supplies make-up liquid to the low pressure side of the transmission. A high pressure relief valve 145 is provided.